EV Adaptive Thermal Management System Optimized to Minimize Power Consumption

ABSTRACT

A method of operating the thermal management system in a vehicle is provided, where the thermal management system includes a heat exchanger (e.g., a radiator) and a heat source (e.g., battery pack, drive train, power electronics, etc.). After characterizing the thermal management system, whenever the system controller issues a cooling demand an appropriate set of operating settings is determined that minimizes the amount of power consumed by the system&#39;s actuators (e.g., blower fan, coolant pump) while still meeting the cooling demand. As a result, the heat source is cooled to the degree required with a minimum expenditure of power, thereby minimizing the impact on driving range and vehicle performance.

FIELD OF THE INVENTION

The present invention relates generally to the thermal management systemof an electric vehicle and, more particularly, to a system and method ofuse designed to adapt the thermal management system to currentconditions in order to minimize power consumption.

BACKGROUND OF THE INVENTION

In response to the demands of consumers who are driven both byever-escalating fuel prices and the dire consequences of global warming,the automobile industry is slowly starting to embrace the need forultra-low emission, high efficiency cars. While some within the industryare attempting to achieve these goals by engineering more efficientinternal combustion engines, others are incorporating hybrid orall-electric drive trains into their vehicle line-ups. To meet consumerexpectations, however, the automobile industry must not only achieve agreener drive train, but must do so while maintaining reasonable levelsof performance, range, reliability, and cost.

Electric vehicles, due to their reliance on rechargeable batteries,require a relatively sophisticated thermal management system to insurethat the batteries remain within their desired operating temperaturerange while still providing adequate heating and cooling within thepassenger cabin and not unduly affecting the vehicle's overall operatingefficiency. A variety of approaches have been taken to try and meetthese goals. For example, U.S. Pat. No. 6,360,835 discloses a thermalmanagement system for use with a fuel-cell-powered vehicle, the systemutilizing both low and high temperature heat transfer circuits thatshare a common heat transfer medium, the dual circuits required toadequately cool the vehicle's exothermic components and heat thevehicle's endothermic components.

U.S. Pat. No. 7,789,176 discloses a thermal management system thatutilizes multiple cooling loops and a single heat exchanger. In anexemplary embodiment, one cooling loop is used to cool the energystorage system, a second cooling loop corresponds to the HVAC subsystem,and a third cooling loop corresponds to the drive motor cooling system.The use of a heater coupled to the first cooling loop is also disclosed,the heater providing a means for insuring that the batteries are warmenough during initial vehicle operation or when exposed to very lowambient temperatures.

U.S. Pat. No. 8,336,319 discloses an EV dual mode thermal managementsystem designed to optimize efficiency between two coolant loops, thefirst cooling loop in thermal communication with the vehicle's batteriesand the second cooling loop in thermal communication with at least onedrive train component such as an electric motor or an inverter. Thedisclosed system uses a dual mode valve system to configure the thermalmanagement system between a first mode and a second mode of operation,where in the first mode the two cooling loops operate in parallel and inthe second mode the two cooling loops operate in series.

Although the prior art discloses numerous techniques for cooling thebattery pack of an electric vehicle, an improved thermal managementsystem is needed that is capable of maintaining the batteries withintheir desired operating temperature range while still providing meansfor optimizing overall vehicle operating efficiency. The presentinvention provides such a thermal management system.

SUMMARY OF THE INVENTION

The present invention provides a method of operating the thermalmanagement system in a vehicle, where the thermal management systemincludes a heat exchanger (e.g., a radiator) and a heat source (e.g.,battery pack, drive train, power electronics, etc.). The method includesthe steps of (i) characterizing the thermal management system, where thestep of characterizing the vehicle thermal management system furthercomprises the step of determining a power dissipation data set for thethermal management system; (ii) determining a power dissipation factordata set based on the power dissipation data set; (iii) determining apower consumption data set corresponding to the thermal managementsystem, where the power consumption data set represents a plurality ofpower consumption datum, and where each of the plurality of powerconsumption datum corresponds to at least one combination of a pluralityof operating settings for the vehicle thermal management system; (iv)characterizing the heat source, where the heat source is thermallycoupled to the thermal management system, where the step ofcharacterizing the heat source further comprises the step of determininga heat source data set, and where the heat source data set is comprisedof a plurality of heat generation datum versus a plurality of heatsource usage datum; (v) periodically determining a cooling demand basedon the heat source usage datum; (vi) determining a power demand based onthe cooling demand; (vii) deriving a subset of the plurality ofoperating settings from the power demand and the power dissipationfactor data set and the power consumption data set, where the subset ofthe plurality of operating settings (e.g., a combination of one of aplurality of blower fan speed settings and one of a plurality of coolantpump flow settings) minimizes power consumption in the thermalmanagement system while meeting the power demand; and (viii) applyingthe subset of the plurality of operating settings to the thermalmanagement system. The method may further include the step of storing ina memory the power dissipation factor data set, the power consumptiondata set and the heat source data set, where the memory is accessible bya thermal management system controller, and where the thermal managementsystem controller performs the steps of periodically determining thecooling demand, determining the power demand, and deriving and applyingthe subset of the plurality of operating settings. The step ofdetermining the power demand may include the step of adding an offset tothe cooling demand.

In one aspect of the method where the power transfer data set iscomprised of a first plurality of power transfer datum, a secondplurality of power transfer datum, and a third plurality of powertransfer datum, the step of determining the power transfer data set mayfurther include the steps of (i) determining the first plurality ofpower transfer datum relative to a plurality of air speeds through theheat exchanger, (ii) determining the second plurality of power transferdatum relative to a plurality of coolant flow rates through the heatexchanger, and (iii) determining the third plurality of power transferdatum relative to a plurality of input temperature differentials for theheat exchanger. Preferably, the step of determining the first pluralityof power transfer datum relative to a plurality of air speeds throughthe heat exchanger is performed while holding constant the coolant flowrate and the input temperature differential; similarly, the step ofdetermining the second plurality of power transfer datum relative to aplurality of coolant flow rates through the heat exchanger is performedwhile holding constant the air speed and the input temperaturedifferential; similarly, the step of determining the third plurality ofpower transfer datum relative to a plurality of input temperaturedifferentials for the heat exchanger is performed while holding constantthe air speed and the coolant flow rate and the ambient temperature. Thepower dissipation factor data set may be comprised of the firstplurality of power transfer datum versus the second plurality of powertransfer datum versus the third plurality of power transfer datum. Thestep of determining the power dissipation factor data set may furthercomprise the step of dividing each of the first, second and thirdpluralities of power transfer datum by a preset power constant (P_(a)),where the preset power constant may be approximately centered within theoperating domain of the thermal management system, and/or may beapproximately centered within the operating domain of the thermalmanagement system's coolant pump, and/or may be approximately centeredwithin the operating domain of the thermal management system's blowerfan.

In another aspect of the method where the thermal management systemincludes a blower fan and a coolant pump, each of the plurality of powerconsumption datum corresponds to the power consumed for a combination ofone of a plurality of blower fan speed settings and one of a pluralityof coolant pump flow settings.

In another aspect of the method where the heat source is comprised of abattery pack containing a plurality of batteries, the step ofcharacterizing the heat source may further comprise the step ofdetermining the efficiency versus the operating temperature for thebatteries. When the heat source is comprised of a battery packcontaining a plurality of batteries, each of the plurality of heatsource usage datum may correspond to a power level demand placed on thebatteries.

In another aspect, the method may further include the steps of (i)monitoring ambient temperature, (ii) monitoring the current coolantinput temperature corresponding to the heat exchanger input, and (iii)determining a current input temperature differential between the ambienttemperature and the current coolant input temperature, where the subsetof the plurality of operating settings is derived from the power demandand the power dissipation factor data set and the power consumption dataset and the current input temperature differential.

In another aspect, the method may further include the steps of (i)monitoring the current coolant input temperature corresponding to theheat exchanger input, (ii) monitoring the current coolant outputtemperature corresponding to the heat exchanger output, (iii)determining the temperature difference between the current coolant inputtemperature and the current coolant output temperature, (iv) monitoringthe current coolant flow rate through the heat exchanger, (v) monitoringthe current air speed through the heat exchanger, and (vi) modifying thepower dissipation factor data set based on the temperature differenceand the current coolant flow rate and the current air speed.

In another aspect of the method where the thermal management systemincludes a blower fan and a coolant pump, the method may further includethe steps of (i) monitoring the blower fan current, (ii) monitoring thecoolant pump current, and (iii) modifying the power consumption data setbased on the blower fan current and the coolant pump current.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be understood that the accompanying figures are only meant toillustrate, not limit, the scope of the invention and should not beconsidered to be to scale. Additionally, the same reference label ondifferent figures should be understood to refer to the same component ora component of similar functionality.

FIG. 1 illustrates an exemplary battery pack cooling system that may beused with the current invention;

FIG. 2 illustrates an alternate battery pack cooling system that may beused with the current invention;

FIG. 3 illustrates an alternate battery pack cooling system that may beused with the current invention, the illustrated system utilizing both aradiator and a heat exchanger as described relative to FIGS. 1 and 2,respectively;

FIG. 4 illustrates the basic methodology of the invention;

FIG. 5 is the experimentally derived characterization curve for anexemplary embodiment, this curve illustrating the relationship betweenpower dissipation and fan speed;

FIG. 6 is the experimentally derived characterization curve for theexemplary embodiment used with FIG. 5, this curve illustrating therelationship between power dissipation and coolant flow rate;

FIG. 7 is the experimentally derived characterization curve for theexemplary embodiment used with FIGS. 5 and 6, this curve illustratingthe relationship between power dissipation and the temperaturedifferential (ΔT);

FIG. 8 illustrates a series of curves based on the characterization datashown in FIGS. 5-7, where each curve represents a different powerdissipation factor relative to air speed and coolant flow rate and inwhich the temperature differential is held constant;

FIG. 9 illustrates a series of power consumption curves of the thermalmanagement system of the exemplary embodiment in which the thermalmanagement system consists of a coolant pump and a blower fan;

FIG. 10 illustrates the application of the methodology of the inventionto the thermal management system shown in FIG. 1 and to a specificcooling demand;

FIG. 11 illustrates the application of the methodology of the inventionto the thermal management system shown in FIG. 1 and to an alternatecooling demand;

FIG. 12 illustrates a modification of the thermal management systemshown in FIG. 1, configured to allow the power dissipation tables to beadjusted in real time; and

FIG. 13 illustrates a modification of the system shown in FIG. 12,configured to allow both the power dissipation tables and the powerconsumption table to be adjusted in real time.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises”, “comprising”, “includes”, and/or“including”, as used herein, specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. As used herein, the term “and/or” and the symbol “/” are meantto include any and all combinations of one or more of the associatedlisted items. Additionally, while the terms first, second, etc. may beused herein to describe various steps or calculations, these steps orcalculations should not be limited by these terms, rather these termsare only used to distinguish one step or calculation from another. Forexample, a first calculation could be termed a second calculation, and,similarly, a first step could be termed a second step, without departingfrom the scope of this disclosure.

In the following text, the term “battery” may refer to any of a varietyof different battery configurations and chemistries. Typical batterychemistries include, but are not limited to, lithium ion, lithium ionpolymer, nickel metal hydride, nickel cadmium, nickel hydrogen, nickelzinc, and silver zinc. The term “battery pack” as used herein refers toone or more batteries, often contained within an enclosure, electricallyinterconnected to achieve the desired voltage and capacity. The terms“electric vehicle” and “EV” may be used interchangeably and may refer toan all-electric vehicle, a plug-in hybrid vehicle, also referred to as aPHEV, or a hybrid vehicle, also referred to as a HEV, where a hybridvehicle utilizes multiple sources of propulsion including an electricdrive system.

Throughout the process of designing and building a car, the engineeringteam must continually balance the various performance and design goalsset for the car with the requirements placed on the car to insure thatthe car can be manufactured at the desired cost. Due to these oftenconflicting requirements, the control system used in a conventionalcar's thermal management system is often quite simple, typicallyutilizing trigger temperatures to activate and deactivate the system'sblower fans and coolant pumps. While the thermal requirements of an EVare more complicated than those of a conventional car due to theinclusion of a battery pack, EV manufacturers continue to use relativelysimple control systems utilizing on/off commands and triggertemperatures. Although such a system may meet the vehicle's thermalrequirements, this form of system control is often quite inefficientfrom a power usage point of view. Recognizing that every system thatdraws power will have an adverse effect on an EV's driving range, andpotentially its performance, the thermal control system of the presentinvention is designed to minimize power consumption while stillachieving the system's thermal goals.

The present invention is not limited to a thermal management systemconfigured in a particular manner; rather the present invention providesa method of minimizing power consumption of virtually any thermalmanagement system. FIGS. 1-3 illustrate three different configurationsfor a vehicle's thermal management system that can be used with thepresent invention. It should be understood, however, that otherconfigurations may be used with the invention and that the invention isnot limited to a particular type of vehicle, i.e., it may be used withan internal combustion engine (ICE) based vehicle, an all-electricvehicle, or a hybrid vehicle. Furthermore, while these exemplary systemsare used to control the temperature of a battery pack, the methodologyof the present invention can be similarly applied to a thermalmanagement system used to control other components and subsystems, forexample drive train components (e.g., engine, motor, transmission, etc.)and/or power electronics (e.g., power inverter, etc.).

FIG. 1 illustrates an exemplary battery thermal management system 100.In system 100, the temperature of the batteries within battery pack 101is controlled by pumping a thermal transfer medium, e.g., a liquidcoolant, through a plurality of cooling conduits 103 integrated intobattery pack 101. Conduits 103, which are fabricated from a materialwith a relatively high thermal conductivity, are positioned within pack101 in order to optimize thermal communication between the individualbatteries, not shown, and the conduits, thereby allowing the temperatureof the batteries to be regulated by regulating the flow of coolantwithin conduits 103 and/or regulating the transfer of heat from thecoolant to another temperature control system. In the illustratedembodiment, the coolant within conduits 103 is pumped through a radiator105 using a pump 107. A blower fan 109 may be used to force air throughradiator 105, for example when the car is stationary or moving at lowspeeds, thus insuring that there is an adequate transfer of thermalenergy from the coolant to the ambient environment. System 100 may alsoinclude a heater 111, e.g., a PTC heater, that may be used to heat thecoolant within conduits 103, and thus heat the batteries within pack101.

FIG. 2 illustrates an alternate battery pack thermal management system200. In system 200 the coolant within conduits 103 is coupled to asecondary thermal management system 201 via a heat exchanger 203.Preferably thermal management system 201 is a refrigeration system andas such, includes a compressor 205 to compress the low temperature vaporin refrigerant line 207 into a high temperature vapor and a condenser209 in which a portion of the captured heat is dissipated. After passingthrough condenser 209, the refrigerant changes phases from vapor toliquid, the liquid remaining at a temperature below the saturationtemperature at the prevailing pressure. The refrigerant then passesthrough a dryer 211 that removes moisture from the condensedrefrigerant. After dryer 211, refrigerant line 207 is coupled to heatexchanger 203 via thermal expansion valve 213 which controls the flowrate of refrigerant into heat exchanger 203. Additionally, in theillustrated system a blower fan 215 is used in conjunction withcondenser 209 to improve system efficiency.

In a typical vehicle configuration, thermal management system 201 isalso coupled to the vehicle's heating, ventilation and air conditioning(HVAC) system. In such a system, in addition to coupling refrigerantline 207 to heat exchanger 203, line 207 may also be coupled to the HVACevaporator 217. A thermal expansion valve 219 is preferably used tocontrol refrigerant flow rate into the evaporator. A heater, for examplea PTC heater 221 integrated into evaporator 217, may be used to providewarm air to the passenger cabin. In a conventional HVAC system, one ormore fans 223 are used to circulate air throughout the passenger cabin,where the circulating air may be ambient air, air cooled via evaporator217, or air heated by heater 221.

In some electric vehicles, battery pack cooling is accomplished using acombination of a radiator such as that shown in FIG. 1, and a heatexchanger such as that shown in FIG. 2. FIG. 3 illustrates such acooling system. In system 300, the coolant passing through battery pack101 via conduits 103 may be directed through either radiator 301 or heatexchanger 203. Valve 303 controls the flow of coolant through radiator301. Preferably a blower fan 305 is included in system 300 as shown,thus providing means for forcing air through the radiator whennecessary, for example when the car is stationary.

In accordance with the invention, and as illustrated in FIG. 4, thefirst step is to independently characterize the heat dissipationqualities of each aspect of the thermal management system (step 401).These heat dissipation qualities are then used to determine the powerdissipation factor for the thermal system under various conditions (step403). Next, the power consumed by the thermal management system usingdifferent settings (i.e., different fan speeds, different pump rates,etc.) is determined (step 405). Additionally, the heat source (e.g.,battery pack, drive train components, power electronics, etc.) ischaracterized (step 407). The results of steps 401, 403, 405 and 407 arestored within a memory accessible by the thermal management system'scontroller (step 409). During vehicle use, the controller determines acooling demand based on current conditions for the heat source, e.g.,based on the current power output of the battery pack (step 411). Apower demand is then calculated (step 413) based on the cooling demandplus a cooling demand offset, where the offset takes into accountcurrent heat source (e.g., battery pack) temperature, ambienttemperature, desired operating temperature, and the thermal mass of theheat source. Based on the power demand, the system controller determinesthe optimum settings for the thermal management system that allowsufficient power to be dissipated in order to cool the heat source tothe desired operating temperature while consuming a minimum amount ofpower (step 415). As a consequence, the heat source (e.g., battery pack)is cooled while using the minimum amount of power required, therebyminimizing the impact on driving range and vehicle performance.

As described above, the present invention provides a method that allowsthe necessary cooling function for a thermal management system to beselected while simultaneously minimizing the power consumed by thesystem's actuators (e.g., blower fan, coolant pump). By minimizing powerconsumption, the process improves overall vehicle efficiency, leading toan increase in driving range when the system is used with an EV. Whileany configuration of thermal management system may utilize the presentmethod, the process is described in detail below for a basic thermalmanagement system that is coupled to a battery pack, e.g., the systemshown in FIG. 1.

Initially each component of the thermal management system ischaracterized by experimentally measuring the power dissipation (i.e.,heat removed) in the heat exchanger in accordance with the equation

P=k _(w) *Q*ΔT _(w),

whereP is the power dissipation in Watts, k_(w) is the heat capacity of thecoolant (e.g., water) in J/(g*K), Q is the mass flow rate of the coolant(e.g., water) in g/s, and ΔT_(w) is the coolant temperature differentialbetween the input and the output of the heat exchanger (e.g., radiator105). For the exemplary system, three different characterizations mustbe made. The first characterization experimentally measures the powerdissipation while changing the air speed by varying the speed of fan109. During this measurement, a constant coolant mass flow rate (Q_(a))is maintained, as is a constant temperature differential between theinput coolant temperature and the ambient air temperature (ΔT_(a)). FIG.5 illustrates this relationship between power dissipation, P, and airspeed, v.

The second characterization experimentally measures the powerdissipation while changing the mass flow rate of the coolant by varyingcoolant pump 107. During this measurement, a constant fan speed (v_(a))is maintained, as is a constant temperature differential between theinput coolant temperature and the ambient air temperature (ΔT_(a)). FIG.6 illustrates this relationship between power dissipation, P, andcoolant flow rate, Q.

The third characterization experimentally measures the power dissipationwhile varying the input coolant temperature relative to the ambienttemperature, i.e., ΔT. During this measurement, a constant coolant massflow rate (Q_(a)) and a constant fan speed (v_(a)) are maintained, as isa constant ambient air temperature. FIG. 7 illustrates this relationshipbetween power dissipation, P, and the input temperature differential,ΔT.

Next, the characterization data for the thermal management system (e.g.,the data shown in FIGS. 5-7 for the exemplary embodiment) is combined inorder to determine the system's power dissipation characteristics. Sincethere are three characteristics that were experimentally derived above,i.e., power dissipation versus air speed, coolant flow rate, and ΔT, athree-dimensional table is derived. FIG. 8 illustrates one ‘slice’ ofthis table, where curves for a series of power dissipation factors(e.g., 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 and 1.4) are shown relative to airspeed (y-axis) and coolant flow rate (x-axis). The ΔT for this slice ofthe table is set at 20° C. It will be understood that other data sliceswould be for different values of ΔT.

In FIG. 8 and in the preferred approach, in order to simplify thecharacterization data, thereby making it easier to utilize, the powerdissipation values, P, are divided by P_(a). Although the value of P_(a)is somewhat arbitrary, it may be defined as the power dissipation levelwhere the three independent variables v, Q and ΔT are equal to v_(a),Q_(a) and ΔT_(a). Preferably P_(a) is selected to be approximatelycentered in the thermal management system's operating domain. The P_(a)used in the present example is shown relative to air speed (v), coolantflow rate (Q), and ΔT in FIGS. 5-7, respectively.

As noted above, the power consumption of the thermal management systemmust also be characterized in order to allow the system to selectoptimum operational settings. FIG. 9 illustrates a plurality of powerconsumption curves (e.g., 50 watts, 100 watts, 150 watts, 200 watts, and250 watts) relative to air speed (y-axis) and coolant flow rate (x-axis)for the exemplary embodiment.

In addition to characterizing the thermal management system, aspreviously noted the heat source must also be characterized. The heatsource in a vehicle may be any subsystem that requires thermalmaintenance, i.e., cooling or heating. Exemplary subsystems include thevehicle's battery pack, engine, motor, gearbox, power inverter, etc. Inthe exemplary configuration used herein to illustrate the methodology ofthe invention, which is based on the thermal management system of FIG.1, the heat source is comprised of a battery pack. To characterize theheat source, the efficiency of the battery pack is determined,preferably as a function of temperature. Other vehicle heat sources(e.g., motor, power electronics, etc.) may be similarly characterized.

Once the thermal management system is completely characterized, both interms of the power factors and the power consumption, and the heatsource is characterized, then characterization tables are stored inmemory (step 409 described above). After the thermal systems of thevehicle have been characterized, the system is able to determine theappropriate settings to maintain the vehicle's heat source at theoptimum operating temperature while minimizing power losses.

In order to select the optimum settings for the thermal managementsystem, a power demand is issued by the vehicle's controller. The powerdemand is selected to maintain the heat source, e.g., the battery pack,within the desired operating range of temperatures. In general, thepower demand is comprised of two parts; the cooling demand and thecooling offset. The cooling demand is based purely on the demands beingplaced on the heat source. For example, if the heat source is a motorwhich is being run at high speeds for an extended period of time, then acooling demand can be derived from the current being drawn by the motorand the efficiency of the motor (which would have been previouslycharacterized). Similarly, in the present example where the heat sourceis a battery pack, the cooling demand can be derived from the presentpower being drawn from the battery pack, modified by the efficiency ofthe battery pack. Generally it can be assumed that the losses due to theinefficiency of the battery pack, or other component, will be expelledas heat.

The cooling offset is used to modify the cooling demand in order tocompensate for modeling uncertainties as well as the lag time requiredto cool (or heat) the battery pack (or other heat source). This lag timeis determined by the thermal properties of the heat source, i.e., thethermal mass of the source, as well as the efficiency of the thermalmanagement system used to control the temperature of the heat source.

Once the power demand is determined from the cooling demand and thecooling offset, the system determines the optimum settings for thethermal management system. Several examples are provided below to insureclarity. It should be understood that the invention is not limited tothe exemplary system described above, nor is it limited to the examplesprovided below. For example, the heat source may be comprised of motors,engines, gearboxes, power electronics, battery packs, etc., either aloneor in combination. Similarly, the characterization curves providedabove, or the values used in the examples, are only meant to illustrate,not limit, the invention.

Example 1

This example is based on the above-defined configuration, i.e., a heatsource comprised of a battery pack and a thermal management system thatincludes a radiator, a coolant pump and a blower fan. For purposes ofthe present example it is assumed that the vehicle is stationary (e.g.,parked) and that the temperature differential, ΔT, between the ambienttemperature and the temperature of the radiator's coolant input is 20°C. Based on the current load on the battery and the pre-determinedcooling offset, the controller in this situation issues a power demandof 4000 watts. Since in the characterization data a P_(a) of 5600 wattswas used, the power demand equates to 4000/5600 or 0.714.

FIG. 10 plots coolant flow rate, Q, against air speed, v. The coolantflow rate is based on the operating range of the coolant pump andtherefore is limited in this example to 4.0 gpm. Since air speedrepresents the speed of the air flowing through radiator 105, it is onlylimited by the capabilities of blower fan 109 when the car is stationaryor moving at low speeds. When the car is traveling at high speed, themotion of the car forces air to pass through the radiator atapproximately the same speed as the car is traveling, therebyeliminating the limitations of the blower fan. In this example, blowerfan 109 is limited to 20 km/hr (line 1001).

Curve 1003 represents the power demand curve set for 0.714. It should beunderstood that in many cases the power demand, i.e., the powerdissipation factor, required by a specific set of conditions may not beincluded in the stored data used by the thermal management system'scontroller to determine appropriate settings. In this situation, therequired power dissipation factor is interpolated from the previouslydetermined data. For example, in the present instance curve 1003 for apower demand of 0.714 is derived from the curves for the powerdissipation factors of 0.6 and 0.8.

The graph of FIG. 10 also includes a series of power consumption curves,specifically the power consumption curves shown in FIG. 9. It should beunderstood that these curves are only representative curves for specificpower consumption levels, i.e., 50, 100, 150, 200 and 250 watts, andthat other levels of power consumption are available up to the limitsimposed by the maximum blower fan output (e.g., 20 km/hr) and themaximum pump rate (e.g., 4 gpm).

The optimal settings for the thermal management system are given by thecrossover point between the power demand curve 1003 and the lowest levelof power consumption available given the limitations of the coolant pumpand the blower fan. In the exemplary embodiment, the lowest level ofpower consumption occurs at point 1005. At location 1005, the coolingdemand placed on the thermal management system by the current conditionswill be met while a minimum amount of power is consumed, specifically 45watts. At crossover point 1005 the coolant pump is operating at itsmaximum capacity, i.e., 4 gpm, while the blower fan is operating atapproximately 5 km/hr. Note that the cooling demands placed on thethermal management system may be met by a wide range of pump and fansettings, but the setting (i.e., crossover point 1005) determined by thepresent method meets this demand while minimizing power consumption.Thus while lower pump speeds and higher fan speeds, such as thoseidentified as crossover points 1007-1011, would cool the battery packand meet the cooling demand in this example, these settings wouldrequire substantially more power, i.e., between 5 watts (crossover point1007) and 200 watts (crossover point 1011) more, than that required byfollowing the methodology of the present invention.

Example 2

This example is based on the same configuration as that used in thefirst example, but assumes that the vehicle is traveling at a rate of 40km/hr and that the difference in temperature (ΔT) between the ambienttemperature and the input of the radiator is 18° C. Based on the currentload on the battery and the pre-determined cooling offset, thecontroller in this situation issues a power demand of 4500 watts which,using a P_(a) of 5600 watts, yields a power demand equivalent to4500/5600 or 0.804.

FIG. 11, as with FIG. 10, plots coolant flow rate, Q, against air speed,v. Curve 1101 represents the power demand curve set for 0.804. Note thatsince ΔT in this example is 18° C., curve 1101 is shifted from the 0.8curve shown in FIG. 8 which was taken with a ΔT of 20° C. Furthermore,since the car is traveling at a rate of 40 km/hr, air is forced throughthe radiator at approximately 40 km/hr (shown as line 1103 in FIG. 11),thereby allowing power to be conserved by turning blower fan 109 off.

Since fan 109 is turned off with the vehicle traveling at 40 km/hr inthis example, the power consumption curves shown in FIG. 11 are basedsolely on the use of pump 107 and as such are represented by verticaldashed lines. In this configuration the optimal setting for the coolantpump is given by the crossover point 1105 between the power demand curve1101 and air speed line 1103. As seen from the figure (see line 1107),crossover point 1105 yields a pump setting that provides a coolant flowrate of approximately 0.6 gpm, and a level of power consumption ofbetween 0.5 and 0.6 watts.

In at least one preferred embodiment, the system is configured tocalculate the actual cooling power in real time, thereby allowing thepower dissipation tables (e.g., FIG. 8 and similar data for other valuesof ΔT) to be adjusted in real time. FIG. 12 illustrates this embodimentbased on the configuration shown in FIG. 1. It should be understood,however, that this same approach can be used equally well with otherconfigurations of the thermal management system, for example thoseconfigurations shown in FIGS. 2 and 3. Additionally, while the exampleemploys a battery pack as the heat source, the heat source may becomprised of any combination of a battery pack, motor, engine, powerelectronic, gearbox, and/or any other component/subsystem used in avehicle that requires cooling.

As shown in FIG. 12, the power dissipation tables (i.e., k_(vQΔT)) 1201is adjusted in accordance with the rule

k _(vQΔT)(v,Q,ΔT)=(1−α)k _(vQΔT)(v,Q,ΔT)+α(k _(w) *Q*ΔT _(w)),

whereα is the adaptation factor. In a preferred embodiment, α is set at 0.05.

FIG. 13 illustrates a modification of the embodiment shown in FIG. 12which is configured to allow the power consumption tables (i.e., thedata shown in FIG. 9) 1301 to be adjusted in real time. As shown,detectors 1303 and 1305 monitor the current draw of coolant pump 107 andblower fan 109, respectively.

Systems and methods have been described in general terms as an aid tounderstanding details of the invention. In some instances, well-knownstructures, materials, and/or operations have not been specificallyshown or described in detail to avoid obscuring aspects of theinvention. In other instances, specific details have been given in orderto provide a thorough understanding of the invention. One skilled in therelevant art will recognize that the invention may be embodied in otherspecific forms, for example to adapt to a particular system or apparatusor situation or material or component, without departing from the spiritor essential characteristics thereof. Therefore the disclosures anddescriptions herein are intended to be illustrative, but not limiting,of the scope of the invention.

What is claimed is:
 1. A method of operating a vehicle thermalmanagement system, said vehicle thermal management system comprising aheat exchanger and a heat source, the method comprising the steps of:characterizing the vehicle thermal management system, wherein the stepof characterizing the vehicle thermal management system furthercomprises the step of determining a power dissipation data set for saidvehicle thermal management system; determining a power dissipationfactor data set based on said power dissipation data set; determining apower consumption data set corresponding to said vehicle thermalmanagement system, wherein said power consumption data set represents aplurality of power consumption datum, and wherein each of said pluralityof power consumption datum corresponds to at least one combination of aplurality of operating settings for said vehicle thermal managementsystem; characterizing said heat source, wherein said heat source isthermally coupled to said vehicle thermal management system, wherein thestep of characterizing said heat source further comprises the step ofdetermining a heat source data set, and wherein said heat source dataset is comprised of a plurality of heat generation datum versus aplurality of heat source usage datum; periodically determining a coolingdemand based on said heat source usage datum; determining a power demandbased on said cooling demand; deriving a subset of said plurality ofoperating settings from said power demand and said power dissipationfactor data set and said power consumption data set, wherein said subsetof said plurality of operating settings minimizes power consumption ofsaid vehicle thermal management system while meeting said power demand;and applying said subset of said plurality of operating settings to saidvehicle thermal management system.
 2. The method of claim 1, furthercomprising the step of storing in a memory said power dissipation factordata set, said power consumption data set and said heat source data set,wherein said memory is accessible by a thermal management systemcontroller, and wherein said thermal management system controllerperforms said steps of periodically determining said cooling demand,determining said power demand, and deriving and applying said subset ofsaid plurality of operating settings.
 3. The method of claim 1, whereinsaid power transfer data set is comprised of a first plurality of powertransfer datum, a second plurality of power transfer datum, and a thirdplurality of power transfer datum, and wherein said step of determiningsaid power transfer data set further comprising the steps of:determining said first plurality of power transfer datum relative to aplurality of air speeds through said heat exchanger; determining saidsecond plurality of power transfer datum relative to a plurality ofcoolant flow rates through said heat exchanger; and determining saidthird plurality of power transfer datum relative to a plurality of inputtemperature differentials for said heat exchanger.
 4. The method ofclaim 3, wherein said step of determining said first plurality of powertransfer datum relative to said plurality of air speeds through saidheat exchanger is performed while holding constant said coolant flowrate and said input temperature differential, and wherein said step ofdetermining said second plurality of power transfer datum relative tosaid plurality of coolant flow rates through said heat exchanger isperformed while holding constant said air speed and said inputtemperature differential, and wherein said step of determining saidthird plurality of power transfer datum relative to said plurality ofinput temperature differentials for said heat exchanger is performedwhile holding constant said air speed and said coolant flow rate and anambient temperature.
 5. The method of claim 3, wherein said powerdissipation factor data set comprises said first plurality of powertransfer datum versus said second plurality of power transfer datumversus said third plurality of power transfer datum.
 6. The method ofclaim 5, wherein said step of determining said power dissipation factordata set further comprises the step of dividing each of said firstplurality of power transfer datum and each of said second plurality ofpower transfer datum and each of said third plurality of power transferdatum by a preset power constant (P_(a)).
 7. The method of claim 6,wherein said preset power constant is approximately centered within anoperating domain of said vehicle thermal management system.
 8. Themethod of claim 6, wherein said vehicle thermal management systemfurther comprises a coolant pump, and wherein said preset power constantis approximately centered within an operating domain of said coolantpump.
 9. The method of claim 6, wherein said vehicle thermal managementsystem further comprises a blower fan, wherein said blower fan isconfigured to force air through said heat exchanger, and wherein saidpreset power constant is approximately centered within an operatingdomain of said blower fan.
 10. The method of claim 1, wherein saidvehicle thermal management system further comprises a blower fan and acoolant pump, and wherein each of said plurality of power consumptiondatum corresponds to power consumed for a combination of one of aplurality of blower fan speed settings and one of a plurality of coolantpump flow settings.
 11. The method of claim 1, said heat sourcecomprising a battery pack, said battery pack comprising a plurality ofbatteries, and wherein said step of characterizing said heat sourcefurther comprises the step of determining an efficiency versus operatingtemperature for said plurality of batteries.
 12. The method of claim 11,wherein each of said plurality of heat source usage datum corresponds toa power level demand placed on said plurality of batteries.
 13. Themethod of claim 1, wherein said step of determining said power demandfurther comprises the step of adding an offset to said cooling demand.14. The method of claim 1, wherein said vehicle thermal managementsystem further comprises a blower fan and a coolant pump, and whereinsaid subset of said plurality of operating settings further comprises acombination of one of a plurality of blower fan speed settings and oneof a plurality of coolant pump flow settings.
 15. The method of claim 1,further comprising the steps of: monitoring an ambient temperature;monitoring a current coolant input temperature corresponding to an inputof said heat exchanger; and determining a current input temperaturedifferential between said ambient temperature and said current coolantinput temperature, wherein said subset of said plurality of operatingsettings is derived from said power demand and said power dissipationfactor data set and said power consumption data set and said currentinput temperature differential.
 16. The method of claim 1, furthercomprising the steps of: monitoring a current coolant input temperaturecorresponding to an input of said heat exchanger; monitoring a currentcoolant output temperature corresponding to an output of said heatexchanger; determining a temperature difference between said currentcoolant input temperature and said current coolant output temperature;monitoring a current coolant flow rate through said heat exchanger;monitoring a current air speed through said heat exchanger; andmodifying said power dissipation factor data set based on saidtemperature difference and said current coolant flow rate and saidcurrent air speed.
 17. The method of claim 1, wherein said vehiclethermal management system further comprises a blower fan and a coolantpump, further comprising the steps of: monitoring a blower fan current;monitoring a coolant pump current; and modifying said power consumptiondata set based on said blower fan current and said coolant pump current.